1. Field of the Invention
The invention relates generally to the field of stackable networking hubs. More particularly, the invention relates to supporting a backplane defined by a stack of networking hubs.
2. Discussion of the Related Art
Prior art networking hubs, sometimes called matrix switches, are known to those skilled in the art. For example, a conventional networking hub is typically stacked with one or more similar hubs to incrementally expand a local area network (LAN).
A problem with this stackable hub technology has been the top layer and the bottom layer in a stack of networking hubs has a different impedance than the middle layers. This impedance mismatch can cause reflection and lose of signal integrity. It is known to couple a terminating resistance to the top and bottom layers in the stack so as to avoid any impedance mismatch. In the past, when a stack is reconfigured, for example via the attachment of one or more additional layers, reconfiguration of the terminating resistance has required skilled personnel and/or complex equipment. Therefore, what is required is a simple solution that automatically reconfigures the terminating resistance.
Another problem with stackable hub technology has been that powering down a layer in a stack of networking hubs can cause an interruption of data flow between other layers in the stack. A stack of networking hubs can include one, or more, unused layers due to fact that under a particular set of circumstances all of the nodes connected to a given layer are not being used or due to the installation of future expansion capacity. If a stack of hubs includes one or more unused layers, it may be desirable to power down the unused hubs. Powering down an unused layer can reduce power consumption and thermal emission. Therefore, what is also required is a solution that provides continuation of data flow between the active layers of a stack, even when one or more other layers in the stack are not powered up.
What is also needed is a solution that is economical to implement. Heretofore, the requirements of automatic impedance matching, powering down one or more layers in a stack without disrupting data flow between other layers in the stack, and economical implementation have not been fully met. What is needed is a solution that simultaneously addresses all of these requirements.